Alpha-D-glucosidase in the serum of the American cockroach, Periplaneta americana
Insect Biochemistry 92: 199-204
An enzyme hydrolyzing oligosaccharide was purified from the serum of the American cockroach by ammonium sulfate precipitation, DEAE cellulose and affinity chromatography. The enzyme hydrolyzed only .alpha.-D-glucosidic linkages of disaccharides other than trehalose and of trisaccharides, enabling classification of the enzyme as .alpha.-D-glucosidase (EC 220.127.116.11). On a polyacrylamide gel, the enzyme activity appeared as a sharp single peak, although the preparation still showed heterogeneity. The Km value for p-nitrophenyl-.alpha.-D-glucopyranoside was 2.8 mM and the pH optimum was 6.8 in 0.2 M phosphate buffer. The physiological roles of this enzyme were discussed in light of experiments on the isolated alimentary canal and the observation that the enzyme was present in the hemolymph of polyphagous insects. For a comparative study, Philosamia cynthia pupae, the larvae of Bombyx mori, Galleria mellonella, Trichiocampus populi, Sarcophaga peregrina and the adults of Tenebrio molitor were used. .